This invention relates to a device for measuring motion of living body organs, such as the heart, and more particularly relates to an improvement of stability and accuracy of measurement of a displacement cardiograph which measures motion of the heart on the body's surface without the use of electrodes.
It is a well-known fact that the oscillation coil of a frequency variable oscillator or detection coil is set on the body's surface and the displacement of the body's surface caused by the motion of the heart is detected as a change of oscillation frequency of the frequency variable oscillator.
Until now, the detector has been composed of a coil 5 and frequency variable oscillator provided with capacitors as shown in FIG. 1 and the oscillating frequency changes when the inductance of coil 5 set on the body's surface changes due to the displacement of the body's surface.
However the frequency of the oscillation circuit composed of a combination of coils and capacitors easily changes due to changes in temperature, moisture or source voltage and consequently, it has been impossible to carry out measurement with repetitive accuracy.